This invention relates to a screening deck consisting of a rigid, frame-like supporting grid, resilient screening elements, forming a composite screen area including protrusions located adjacent one another which project from the edge of the screen elements through holes in the cross-bars of the support frame, whereby the protrusions of neighbouring elements are releasably secure the screening elements to the support frame, with this arrangement, it is possible to replace individual screen elements which become worn without replacing the entire screen.
A screen deck of this type is described in DT-OS 24 37 809 wherein the protrusions on the underside take the form of latch buttons. The screening elements are secured to the support frame by means of clip or snap connections for which adjacent elements must be held together before being fitted to the grid in order that the respective protrusions may together form a complete latch button which can then be pushed through the aperture in the bar of the support frame. This poses the difficulty that the elements can only be fitted to the support frame with difficulty because the adhesion and cohesion of the abutting surfaces of the parts forming together a latch button prevent relative movement of adjacent parts. Finally, because of the clip or snap effect, an especially high surface pressure occurs between the abutting faces of adjacent protrusions. For this reason, a subsequent replacement of single screen elements is very difficult. Slots can be provided in the wide heads of the protrusion so that they may be pressed together and withdrawn through the apertures in the support frame, but the retaining effect is thereby greatly reduced. In practice it is usual to cut off the heads of the protrusions of the element which is to be replaced below the support frame so that the screen element can then be removed. Damage to the removed element can hardly be avoided, so that re-use of an exchanged element is often no longer possible. The known screens, therefore, are not suitable for repeated replacement of the screen elements, whereby the elements may be re-fitted in the same or another position on the grid.
Furthermore, it is also known to provide screen decks with resilient screening elements which are secured to a rigid carrier grid. The support-bars are provided with apertures through which screws embedded in the screen element are passed and secured from below by means of screw nuts ("Aufbereitungstechnik", 8/1967, from page 646 on, and "Aufbereitungstechnik", 11/1970, from page 383 on.). Replacing individual screening elements on this kind of screening surface is even more complicated because special tools are needed for fitting and removing the securing screws, which are subject to corrosion problems.
Screening decks with resilient synthetic screening elements are also known, wherein the edges of the screening elements are provided with mushroom shaped protrusions which fasten like press studs in connecting bars arranged between the screen elements (DT-AS 1 814 839). The anchor-like protrusions are arranged parallel to the plane of the screen elements, and the overlap at the sides is compensated for by the connecting bar. The purpose of the invention therefore, is to provide a screening deck of the type described which, in place of the snap connections, provides protrusions in the form of locating means on the under side of the screen element, and separate securing means therefor.